1. Field of the Invention
The present invention relates to a TDMA mobile communication system for transmitting data therefrom and receiving the same therein in accordance with a TDMA method, and particularly to an RF power level monitoring apparatus suitable for use in a TDMA mobile communication system.
2. Description of the Prior Art
FIG. 6 is a view showing the structure of an RF power level monitoring apparatus which has conventionally been employed in an analog mobile communication system. In FIG. 6, reference numeral 121 indicates a CPU of the analog mobile communication system and reference numeral 123 indicates a transmitter including an unillustrated transmission and reception antenna. Further, reference numeral 124 indicates an A/D converter for converting an RF power level of a transmission signal frequency-converted into an RF band and whose power has been amplified, into a digital value.
In order to measure an analog level of a signal sent from the transmitter 123, the CPU 121 outputs a triggering signal to the A/D converter 124. The A/D converter 124 converts the analog level of the signal sent from the transmitter 123 into digital data in response to the triggering signal supplied from the CPU 121. After the conversion of the analog level into the digital data has been completed, the A/D converter 124 delivers a conversion end signal indicative of its completion to the CPU 121. When the CPU 121 recognizes the delivery of the conversion end signal from the A/D converter 124, the CPU 121 reads the digital data converted by the A/D converter 24 and makes a decision as to whether or not the analog level of the signal transmitted from the transmitter 123 is normal.
If it is decided that the analog level of the signal is in an improper state, then the CPU 121 displays the contents of its improper state on a display device of the analog mobile communication system. Sequentially the CPU 121 turns off an RF power amplifier or sends a signal indicative of its improper state to a system connected to the analog mobile communication system.
When the conventional power level monitoring apparatus having the above-described construction is applied to the analog communication system whose output to be transmitted is constant, the transmission power can be monitored accurately. However, a transmission signal is burst-transmitted during a few msec in a TDMA (Time Division Multiple Access) system. Therefore, the power to be transmitted cannot be measured with accuracy when the aforementioned power monitoring apparatus is used.